I'm preparing for my exams I stumbled across this exercise. Now I can't seem to figure it out. Anybody can help me ?
The exercise:
For the 8bit data word: 00111001 the check bits are: 0111. Now if the word is read from the memory and the check bits are 1101, what is the dataword?
The text is translated from another language to English.
I started by doing a check :
The entire word is the dataword (8 bits) combined with the check (4 bits).
In this case: 0 0 1 1 0 1 0 0 1 1 1 1 (the check bits on position 1, 2, 4 and 8, with the right bit being the least significant bit)
Then the check itself:
The check consists of searching for all the bit that have the value one from the dataword in the combined word. It can be seen that position 3 7 9 and 10 have the value one and didn't come from the check. These 4 values are written binary and added up. When this is done. the check is found again. (To confirm that this method works)
3: 0 0 1 1
7: 0 1 1 1
9: 1 0 0 1
10: 1 0 1 0
0 1 1 1
So this is correct (Just to see if this method is correct)
Then I have another check (1101), but how can I find the data word ?
Thx in advance